Monochannel propagation mechanism in transformer oil at low breakdown probabilities

It is found that the channel´s development character in oil in the vicinity of the minimum breakdown voltage is stepped. The channel moves discretely with the ionization zone length concentrated at the top of the channel. The similarity in the discharge development processes under low breakdown probabilities and high overvoltages shows that the stepped process is fundamental and inherent to the channel development in oil. Experimental data estimate the energy density for the channel unit generation. The results show that the main process is field ionization, while others are connected with the phase transition, channel substance formation and hydrodynamic phenomena